/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Selection/MeshTopologySelectionMechanic.h
Perform a hit test on the topology using the current selection settings. In cases of hitting edges and corners, OutHit contains the following: OutHit.FaceIndex: edge or corner id in the topology OutHit.ImpactPoint: closest point on the ray to the hit element (Note: not a point on the element!) OutHit.Distance: distance along the ray to ImpactPoint OutHit.Item: if hit item was an edge, index of the segment within the edge polyline. Otherwise undefined.
bool TopologyHitTest ( const FRay & WorldRay, [FHitResult](API\Runtime\Engine\Engine\FHitResult) & OutHit, bool bUseOrthoSettings )